Nuclear magnetic resonance (NMR) spectroscopy is being used to study the state of Na ions in tissue. Relaxation times are being measured by appropriate pulse techniques. The research is being undertaken to determine whether or not 23Na resonances can be utilized to detect changes in intracellular ions and water. As a model system, bacteria are dispersed in solutions of sodium chloride. The Na ions interact with the cell surfaces and the interaction is detected as changes in relaxation time. This model is being used to define the mechanisms leading to changes in relaxation times. Proton spectra of water in tumor tissue originally demonstrated that the state of water, as detected by NMR, could be altered by the pathologic condition. We are comparing 23Na spectra with those of water protons to see of Na ions will also reflect an abnormal state of intracellular fluids. Tumors and transformed cell lines are being investigated.